Recovery of manganese from metallurgical slags, dusts, and ores



3,028,233 RECOVERY oF MANGANESE FROM METALLURGICAL D1 RANA. E ,m Emy AwaHDM c@ S51 .mi CLF .S J

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. S Eg www VE O EE@ oo Nw mm J l Mm VIJIIIIJ ME Y B Q; @N E @n mE/mw. 4@N\ -Smmwm Em :dffwwwmr @E Q: N UI @2 5/m: N mia II|\ mm m32/ M651@3,028,233 RECUVERY F MANGANESE FRM METALLUR- GlCAL SLAGS, DUSTS, AND@RES .lames C. Schaefer, North Roy-alten, and Ernest C. Schmidt, Euclid,Ghia, assiguors to Walter M. Weil, Shaker Heights, Ohio Filed May 31,1960, Ser. No. 32,910 Claims. (Cl. "iS-112) This invention relates tothe recovery of substantially pure manganese from metallurgical dusts,slags, and natural and synthetic ores containing manganese in the formof metal or oxide, or both, generally in admixture with relatively largequantities of undesired materials such as carbon, oxides of alkalimetals, alkaline earth metals, iron, aluminum, silicon, and the like.The invention is particularly suited for the recovery of manganese fromso-called precipitator dusts collected in the course of variousmetallurgical operations, such as the production of steel. However, theinvention is also applicable to the recovery of manganese frommetallurgical slags and natural and synthetic ores in which the commonlyoccurring undesired materials are present in varying quantities comparedto the manganese content.

In Patent No. 2,877,110 of Cooper, Schaefer, and Schmidt, a process isdisclosed for the recovery of manganese from the above-described dusts,slags, and ores. ln accordance with that patent, the iron, alkalineearth metals, and gangue are iirst removed by a series of stepsincluding chloridizing and leaching operations, leaving a mixture ofalkali metal chlorides and manganese chloride. The production of thismixture of manganese chloride and alkali metal chlorides was consideredto be one of the advantages of the process of the Cooper et al. patentbecause commercially feasible fused salt bath electrolysis of manganesechloride was thought to require the employment of alkali metal chloridesin the bath as a vehicle for the manganese chloride.

In accordance with the present invention, at least a portion, andpreferably substantially all, of the alkali metal chlorides areseparated from the manganese compounds at an early stage in the process.The removal of at least a portion of the alkali metal chlorides at anearly stage provides a number of advantages not attainable by theprocess of the Cooper et al. patent or by any other known processes. Forexample, it is not necessary to heat and dry the alkali metal chloridesremoved by the present invention, thereby saving a substantial amount ofthe heat energy formerly necessary to dry the salt mixture forelectrolysis. Moreover, we have now found that, by eliminating thealkali metal chlorides from the fused bath in the electrolytic cell, thefused salt electrolysis may be conducted at lower temperatures withconsiderable savings in heat energy and no reduction in electricalefficiency or product purity or other undesirable results. In addition,the bath may be operated for longer electrolysis periods withoutinterruption, and in some cases, substantially continuously, because thebuild-up of alkali metal chlorides in the cell isgreatly reduced.

The separation of at least a portion of the alkali metal chlorides fromthe manganese chloride is accomplished in the process of the presentinvention after the iron, alkaline earth metals, and gangue have beenremoved in the manner described in Cooper et al. Patent No. 2,877,110.

The iron is removed during the chloridizing of the mass by maintainingthe temperature above about 315 C. Above this temperature, the ferriechloride formed during the chloridizing step sublimes and is withdrawnfrom the reaction chamber and condensed in conventional condenserapparatus.

During the chloridizing step, the manganese and alkali metal compoundsare also converted to chlorides,.while 3,523,233 Patented Apr. 3, 1962ICC the alkaline earth metal compounds and other gangue remainunconverted. Advantageously, the temperature is maintained below themelting point of manganese chloride (about 650 C.) during thechloridizing of the manganese and alkali metal compounds. In thismanner, the corrosion problems encountered in the handling of moltenmanganese chloride are avoided.

Since the manganese and alkali metal chlorides formed during thechloridizing step are soluble in hot water, the reaction mass remainingafter the sublimation of the ferrie chloride is leached with hot waterto dissolve the manganese and alkali metal chlorides. After thesechlorides have been dissolved, the slurry maybe filtered to remove thealkaline earth metal compounds and other gangue which are insoluble inthe hot Water.

To separate the alkali metal chlorides from the manganese chloride, theleach liquor is treated to precipitate the alkali metal chlorides whileallowing the manganese chloride to remain in the solution. This may beaccomplished either by cooling the leach liquor, -by adding hydrogenchloride to the liquor, or by a combination of these steps.

lf the alkali metal chlorides are removed by the addition of hydrogenchloride, the hydrogen chloride or aqueous solution thereof(hydrochloric acid) which is recovered from the liquor during theevaporating step subsequent to the removal of the alkali metalchlorides, may be recycled for use in the treatment of additionalquantities of leach liquor.

Advantageously, substantially all of the alkali metal chlorides areseparated from the manganese chloride solution at this point. However,the benets derived from employing the process of the present inventionare still achieved, but to a lesser degree, when only a portion of thealkali metal chlorides are removed.

The process of the invention will be more fully described with referenceto the accompanying drawing. It will be apparent from the followingdescription that various steps of the process are not critical and maybe performed in a number of generally equivalent ways. Accordingly, thedetails of such steps, for the most part, are shown in a schematicmanner in the drawing.

The starting manganese-containing material 1 is fed into a suitablepreliminary drying device 2 from which the dried material is fed,intermittently or continuously, into 'a reactor 3. Although the dryingstep is usually necessary to remove the moisture from the charge, it maybe omitted if the material being processed is substantially moisturefree. In the reactor, the dried materialto be processed for the recoveryof manganese is subjected to a chloridizing operation.

The dried material fed into the reactor generally is heated to thedesired temperature range between about 315 and 650 C. before thegaseous chloridizing agent is introduced into the reactor from a source4 through conduits 6 and 7. The chloridizing agent is preferablychlorine gas, although other chloridizing materials which produce ferricchloride may be employed.

As the ehloridizing agent -reacts with the iron present in the driedmaterial, ferrie chloride is formed which volatilizes since thetemperature of the reactor is above 315 C. The gaseous ferrie chloridepasses out of the reactor through a conduit 8 into a condenser 12 whereit is condensed. Any non-condensable gases in the gaseous stream fromreactor 3, including any excess chlorine which may be present, are notcondensed in condenser 12 but passed therethrough and out through aconduit 13. When an appreciable amount of excess chlorine is present,the gaseous 4stream may be returned to reactor 3 through a conduit 18(shown by dotted lines in the drawing) and the conduit 7.

Since the temperature of the reaction mass need only be .above 315 C. tosublime the ferrie chloride formed, the chloridizing operation, ifdesired, may be started when this temperature is reached but before thetemperature in the reactor h-as attained the desired manganese reactiontemperature. As the heating continues, the temperature will approach the650 C. maximum speciiied above. Maintaining the temperature Vat or closeto this higher .level accelerates the chloridizng of the manganese andalkali metal constituents of the mass.

The time required to complete the removal of the iron from the dried`material and that necessary to chloridize the managese and alkali metalconstituents will vary with the temperature employed, the size,composition, and porosity of the charge, the nate of ow of thechloridizing agent, and other factors.

When the chloridizing of the alkali metal constituents is substantiallycomplete, the reaction mass is removed from the reactor and transferredto a suitable leaching apparatus 21. The water employed for leaching themass is maintained at an elevated temperature to dissolve the manganeseand alkali metal chlorides formed during the chloridizing operation.Advantageously, the slurry is agitated to facilitate dissolution of thesoluble chlorides.

Since the alkaline earth metal and other gangue constituents are notconverted to chlorides during the chloridizing operation, thesematerials are not dissolved in the leaching apparatus. After thedissolution of the soluble constituents is substantially complete, theslurry is transferred to a suitable liquid-solids separator, for example, a filter 24, to separate the undissolved `alkaline earth metalconstituents and gangue yfrom the dissolved chlorides.

The iiltrate comprising substantially exclusively dissolved manganesechloride and alkali metal chlorides is then treated in a suitableprecipitation apparatus 25 to precipitate the alkali metal chlorides. Aspointed out above, this precipitation may be accomplished by cooling thefiltrate, by the addition of hydrogen chloride, or by a combination ofthese steps.

After Iall or a desired proportion of the alkali metal chlorides havebeen precipitated, the precipitated salts are separated from the liquorby a suitable liquid-solids separator, for example, a lter 26. Theremaining liquor is then transferred to an evaporator 23 where the waterand 'any hydrogen chloride are removed leaving crystallized manganesechloride. The manganese chloride salt is then dried in a suitable dryingdevice 29 to remove the remaining moisture `and any hydrogen chlorideoccluded in the salt.

The hydrogen chloride gas recovered from the evaporator vand drier maybe recycled to precipitate additional quantities of the alkali metalchloride in the liquor. In addition, the alkali metal chloride separatedfrom the liquor, if desired, may be reacted with concentrated sulfurieacid to form quantities of hydrogen chloride which also may be employedto precipitate additional alkali metal chlorides in precipitationapparatus 25. The alkali metal sulfate luy-products formed may be sold`as an ingredient for fertilizers.

The dried manganese chloride salt may be dissociated to recovermanganese metal by any of the applicable methods Vknown in the art. Forexample, the manganese chloride may be reduced with hydrogen to formmanganese metal, as described in Kinney Patent No. 2,290,843. In thatcase, the hydrogen chloride gas formed as a by-product in the processmay be recycled for use in the precipitation of additional alkali metalchlorides, as described above.

Particularly advantageous results are achieved when the manganesechloride salt is dissociated by fused salt electrolysis. By this method,the dried manganese chloride with or Without some alkali metal chloridesmay be charged into an electrolytic cell of the fused salt bath typeshown in the drawing as cell 30.

A suitable electrolytic cell for the purpose of invention may comprise asimple heat-resistant iron alloy pot 31 constituting the cathode and acarbon rod 32 suspended in the bath constituting the anode. Electricalleads 33 and 34 connect the anode and cathode to the appropriateterminals of a motor generator set 35. The voltage applied may be variedalong with the spacing of the anode and cathode to provide a suitablecurrent iiow.

Dissociation of the manganese chloride in the electrolytic cell releaseschlorine from the anode in a substantially completely anhydrous formwhich is suitable for recirculation through conduit 6 for use in thechloridizing step taking place in reactor 3. I-f a substantialproportion of alkali metal chlorides is present in the charge to theelectrolytic cell, the concentration of these chlorides will build up inthe bath as electrolysis continues necessitating the periodicinterruption of the electrolysis to remove the accumulated alkali metalchlorides. Thus, as pointed out above, the removal of substantially allof the alkali metal chlorides during the cooling or HC1 treatmentpermits longer electrolysis periods without interruption.

The manganese deposited on the cathode as indicated at 36 may be removedfrom the electrolytic cell at suitable intervals and transferred Whilestill hot to a heated centrifuge 37 to separate entrained molten alkalimetal chloride from the solid manganese metal.

By means of the process described, from to 95% or more of the manganesecontent of precipitator dusts may be recovered as manganese metal of apurity around 98% or better, depending on the inal puriiicationprocedure employed. If high purity is not of great importance andappreciable surface oxide is not objectionable, the manganese granulesmay simply be recovered from the electrolytic cell. Obviously, ifdesired, other recovery and inal purification procedures may beperformed on the metal product of the electrolytic cell, according toany special requirements of particular end uses for which the metalproduct is intended.

As indicated above, the process is equally applicable to the recovery ofmanganese from a variety of ores, metallurgical slags and tailings, andsimilar materials containing appreciable amounts of manganese, with orWithout iron in almost any proportion.

From the above description, it is apparent that the process of thepresent invention provides a highly eficient process for producingsubstantially pure manganese from metallurgical dusts, slags, andsimilar materials. Moreover, the process of the invention permits aconsiderable savings in heat energy since the alkali metal carrier saltsare removed at an early stage in the process. Furthermore, the removalof these alkali metal salts prior to the electrolysis step, permitslonger electrolysis periods and, in some cases, substantially continuousoperations of the electrolytic cell.

As will be apparent from the foregoing specification, the invention isnot limited to the specic details of manipulative operations, reagentsand apparatus speciiically shown or described, but is subject tonumerous modifications without departing from the invention as dened inthe appended claims.

What is claimed is:

1. A process for recovering manganese values in useful form frommaterials containing manganese as metal, or as oxide, or both togetherwith gangue materials including alkali metal oxides, the processcomprising contacting a mass of such material With a gaseouschloridizing agent containing free chlorine, at a temperature belowabout 650 C. to convert the manganese to manganese chloride and thealkali metal to alkali metal chloride, leaching the mass With Water todissolve manganese and alkali metal chlorides from insoluble componentsof the mass, separating the chloride leach liquor from the insolublecomponents, treating said leach liquor to precipitate at least a portionof the alkali metal chloride dissolved therein, separating theprecipitated .alkali metal chloride and removing water from theremaining liquor to recover manganese chloride.

2. In a process for recovering manganese values in useful form frommaterials containing manganese as metal, or as oxide, or both togetherwith gangue materials including alkali metal oxides, which processcomprises contacting a mass of such material with a gaseous chloridizingagent containing free chlorine, at a temperature below about 650 C. toconvert the manganese to manganese chloride and the alkali metal toalkali metal chloride and leaching the mass with water to dissolvemanganese and alkali metal chlorides from insoluble components of themass, the steps comprising separating the chloride leach liquor from theinsoluble components, treating said leach liquor to precipitate at leasta portion of the alkali metal chloride dissolved therein, separating theprecipitated alkali metal chloride, removing water from the remainingliquor to recover manganese chloride, and dissociating said manganesechloride to form manganese metal.

3. A process for recovering manganese values in useful form frommaterials containing manganese as metal, or as oxide, or both togetherwith gangue materials including alkali metal oxides, the processcomprising contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature belowabout 650 C. to convert the manganese to manganese chloride and thealkali metal to alkali metal chloride, leaching the mass with water todissolve manganese and alkali metal chlorides from insoluble componentsof the mass, separating the chloride leach liquor from the insolublecomponents, treating said leach liquor to precipitate at least a portionof the alkali metal chloride dissolved therein, separating theprecipitated alkali metal chloride, removing water from the remainingliquor to recover manganese chloride-containing solids, electrolyzingsaid manganese chloride-containing solids in a fused salt bath todeposit manganese as metal, and separating the manganese metal from thefused salt bath.

4. A process for recovering manganesevalues in useful form frommaterials containing manganese and iron as metals, or as oxides, or bothtogether with gangue materials including alkali metal oxides, theprocess comprising contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature betweenabout 315 and 650 C. to convert the manganese to manganese chloride, theiron to ferrie chloride, and the alkali metal to alkali metal chloride,separating the ferrie chloride by sublimation without appreciable fusionor volatilization of the manganese and alkali metal chlorides, leachingthe mass with Water to dissolve manganese and alkali metal chloridesfrom insoluble components of the mass, separating the chloride leachliquor from the insoluble components, treating said leach liquor toprecipitate at least a portion of the alkali metal chloride dissolvedtherein, separating the precipitated alkali metal chloride, and removingwater from the remaining liquor to recover manganese chloride.

5. A process for recovering manganese values in useful form frommaterials containing manganese as metal, or as oxide, or both togetherwith gangue materials including alkali metal oxides, the processcomprising contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature belowabout 650 C. to convert the manganese to manganese chloride and thealkali metal to alkali metal chloride, leaching the mass with water todissolve manganese and alkali metal chlorides from insoluble componentsof the mass, separating the chloride leach liquor from the insolublecomponents, cooling said leach liquor to precipitate at least a portionof the alkali metal chloride dissolved therein, separating theprecipitated alkali metal chloride, and removing water from theremaining liquor to recover manganese chloride.

6. A process for recovering manganese values in useful form frommaterials containing manganese as metal, or as oxide, or both togetherwith gangue materials including alkali metal oxides, the processcomprising contacting a mass of such material With a gaseouschloridizing agent containing free chlorine, at a temperature belowabout 650 C. to convert the manganese to manganese chloride and thealkali metal to alkali metal chloride, leaching the mass with water todissolve rmanganese and alkali metal chlorides from insoluble componentsof the mass, separating the chloride leach liquor from the insolublecomponents, adding hydrogen chloride to said leach liquor to precipitateat least a portion of the alkali metal chloride dissolved therein,separating the precipitated alkali metal chloride, and removing liquidfrom the remaining liquor to recover manganese chloride.

7. A process for recovering manganese values in useful form frommaterials containing manganese as metal, or `as oxide, or both togetherwith gangue materials including alkali metal oxides, the processcomprising contacting `a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature belowabout 650 C. to convert the manganese to manganese chloride and thealkali metal to alkali metal chloride, leaching the mass with water todissolve manganese and alkali metal chlorides from insoluble componentsof the mass, separating the chloride leach liquor from the insolublecomponents, adding hydrogen chloride to said leach liquor to precipitateat least a portion of the alkali metal chloride dissolved therein,separating the precipitated alkali metal chloride, removing water andhydro gen chloride from the remaining liquid to recover manganesechloride, and adding the hydrogen chloride removed to additionalquantities of leach liquor to precipitate alkali metal chloride.

8. A process for recovering manganese values in useful form frommaterials containing manganese and iron as metals, or as oxides, or bothtogether with gangue materials including alkali metal oxides, theprocess comprising contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature betweenlabout 315 and 650 C. to convert the manganese to manganese chloride,the iron to ferrie chloride, and the alkali metal to alkali metalchloride, separating the ferric chloride by sublimation withoutappreciable fusion or volatilization of the manganese and alkali metalchlorides, leaching the mass with ywater to dissolve manganese andalkali metal chlorides from insoluble components of the mass, separatingthe chloride leach liquor from the insoluble components, cooling saidleach liquor to precipitate at least a portion of the alkali metalchloride dissolved therein, separating the precipitated alkali metalchloride, removing water from the remaining liquor to recover manganesechloride-containing solids, electrolyzing said manganesechloride-containing solids in a fused salt bath to deposit manganese asmetal, and separating the manganese metal from the fused salt bath.

9. A process for recovering manganese values in useful form frommaterials containing manganese and iron as metals, or as oxides, or bothtogether with gangue materials including alkali metal oxides, theprocess comprising contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, at a temperature betweenabout 315 and 650 C. to convert the manganese to manganese chloride, theiron to ferrie chloride, and the alkali metal to alkali metal chloride,separating the ferrie chloride by sublimation without appreciable fusionor volatilization of the manganese and alkali metal chlorides, leachingthe mass with water to dissolve manganese and alkali metal chloridesfrom insoluble components of the mass, separating the chloride leachliquor from the insoluble components, adding hydrogen chloride to saidleach liquor to precipitate at least a portion of the alkali metalchloride dissolved therein, separating the precipitated alkali metalchloride, removing Water and hydrogen chloride from the remaining liquorto recover manganese chloride-containing solids, electrolyzing saidmanganese chloride-containing solids in a fused salt bath `to depositmanganese as metal and release chlorine, separating the manganese metalfrom the fused salt hath, and utilizing the released chlorine tochloridize additional material in the process.

li). ln a process for recovering manganese values in useful form frommaterials containing manganese and iron as metals, or as oxides, or bothtogether with gangue materials including alkali metal oxides, whichprocess comprises contacting a mass of such material with a gaseouschloridizing agent containing free chlorine, `at a temperature betweenabout 315 and 650 C. to convert the manganese to manganese chloride, theiron to ferrie chloride, and the alkali metal to alkali metal chloride,separating the ferrie chloride by sublimation without appreciable fusionor volatilization of the manganese and alkali metal chlorides, leachingthe mass with water to dissolve manganese and alkali metal chloridesfrom insoluble components of the mass and separating the chloride leachliquor from the insoluble components, the steps comprising addinghydrogen chloride to said leach liquor to precipitate at least lavportion of the alkali metal chloride dissolved therein, separating theprecipitated alkali metal chloride, removing water and hydrogen chloridefrom the remaining liquor to recover manganese chloride-containingsolids, adding the hydrogen chloride removed to additional quantities ofleach liquor to precipitate alkali metal chloride, electrolyzing saidmanganese chloride-containing solids in a fused salt bath to depositmanganese as metal and release chlorine, separating the manganese metalfrom the fused salt bath, and utilizing the released chlorine tochloridize additional material in the process.

Mitchell Aug. 19, 1930 Cooper et al. Mar. l0, 1959

10. IN A PROCESS FOR RECOVERING MANGANESE VALUES IN USEFUL FORMMATERIALS CONTAINING MANGANESE AND IRON AS METALS, OR AS OXIDES, OR BOTHTOGETHER WITH GANGUE MATERIALS INCLUDING ALKALI METAL OXIDES, WHICHPROCESS COMPRISES CONTACTING A MASS OF SUCH MATERIAL WITH A GASEOUSCHLORIDIZING AGENT CONTAINING FREE CHLORINE, AT A TEMPERATURE BETWEENABOUT 315* ANDF 650*C. TO CONVERT THE MANANESE TO MANGANESE CHLORIDE,THE IRON TO FERRIC CHLORIDE, AND THE ALKALI METAL TO ALKALI METALCHLORIDE, SEPARATING THE FERRIC CHLORIDE BY SUBLIMATION WITHOUTAPPRECIABLE FUSION OR VOLITILLIZATION OF THE MANGANESE AND ALKALI METALCHLORIDES, LEACHING THE MASS WITH WATER TO DISSOLVE MANGANESE AND ALKALIMETAL AND SEPARATING FROM INSOLUBLE COMPONENTS OF THE MASS ANDSEPARATING THE CHLORIDE LEACH LIQUOR FROM THE INSOLUBLE COMPONENTS, THESTEPS COMPRISING ADDING HYDROGEN CHLORIDE TO SAID LEACH LIQUOR TOPRECIPITATE AT LEAST A PORTION OF THE ALKALI METAL CHLORIDE DISSOLVEDTHEREIN, SEPARATING THE PRECIPITATED ALKALI METAL CHLORIDE, REMOVINGWATER AND HYDROGEN CHLORIDE FROM THE REMAINING LIQUOR TO RECOVERMANGANESE CHLORIDE-CONTAINING SOLIDS, ADDING THE HYDROGEN CHLORIDEREMOVED TO ADDITIONAL QUANTITIES OF LEACH LIQUOR TO PRECIPITATE ALKALIMETAL CHLORIDE, ELECTRLYZING SAID MANAGANESE CHLORIDE-CONTAINING SOLIDSIN A FUSED SALT BATH TO DEPOSIT MANAGANESE METAL FROM THE FUSED SALTBATH SEPARATING THE MANGANESE METAL FROM THE FUSED SALT BATH, ANDUTILIZING THE RELEASED CHLORINE TO CHLORIDIZE ADDITIONAL MATERIAL IN THEPROCESS.